Integrated circuit controllers are widely used in power management applications such as regulated power supplies, battery chargers and the like. The general trend has been to design such circuits to accomplish more of the control functions required in a wider variety of applications to reduce component count and design time, or to provide greater versatility. Product designers are often faced with tradeoffs of desired features with cost objectives.
One problem heretofore unmet in a battery charger application, for example, is providing for control of the timing of a plurality of battery charging modes including fast charge, trickle charge and topoff charge. Various types of battery chemistry and discharge history require different timing of each of these modes to tailor the battery charging operation to a particular type of battery. Typically, several external time references connected to several IC pins may be required to accomplish the desired result.
Another problem found in the exemplary battery charger or other power supply regulator applications is providing a controller that is responsive to both polarities of the load current feedback signal without duplicating sensing circuitry. Typically, this requirement is met by separate amplifiers and references for each polarity which add cost to the system. Further, moving the sense resistor from one lead of the battery to be charged to the other lead ordinarily requires a different circuit design. Alternatively, changing the terminal in the circuit where system ground and chip ground are tied together may also require different circuitry. It would be useful to provide a single controller design with several options for locating the current sense resistor or referencing the control circuit ground in a variety of applications.
Thus, several primary objectives of circuit designers are to provide maximum functionality in a circuit controller without requiring a large number of terminals to interface with input and output components. These goals are typically met in an integrated circuit, for example, by limiting the number of required external components to those that are virtually impossible to fabricate on an integrated circuit. Heretofore, these objectives have been difficult to achieve while accommodating different types of battery charger or regulator circuits.